I believe you're only asked to provide the old one if you recently changed. I've had friends come in on tourist visas who have just had their passports replaced and had to show their old ones too. A real pain.

A co-worker did a HK Z-visa run a fortnight ago and didn't need their old passport.

your z visa paperwork from kunming needs to state that you will be going to hk/chiang mai etc. for your visa. then hk/chaing mai will issue it. you need to speak to your employer about getting this done

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GoKunming is the online resource for Yunnan Province and its capital city, Kunming. We offer up-to-date information regarding events, local businesses, news, nightlife and travel, as well as incredibly active user-generated classified and forum sections. GoKunming is southwest China’s largest and best English-language website.